Even if you run a firewall, keep your virus definitions updated, and don't run attachments that are e-mailed to you, you may still be at risk. Browser vulnerabilities can allow intruders into your system or allow your private data to be read just by viewing a webpage. What follows are a series of browser security tests to see whether you are vulnerable. You can either start at the beginning and run through them all, or jump to a test by using the table of contents.